Signaling by high-frequency waves



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Patented Jan. 1, 1 324.

lglldlt UNETED STAT ES PATENT Ol FlfiE.

EDVARD O. SCRIVEN, OF NEW YORK, N. Y., ASSIGNOR TO 'WE STERN ELECTRICCOLL PANY, INCORPORATED, OF NEW YORK, N. 'Y., ACGRPORATION OF NEW YORK.

SIGNALING BY HIGH-FREQUENCY waves.

Application filed September 29, 1919. Serial No. 327,038.

To (ZZZ whom it may concern:

Be it known that I, EDWARD O. SCRIVEN, a citizen of the UnitedStates,residing at New York, in the county of New York, State of 6 NewYork, have invented certain new and useful Improvements in Signaling byHigh- Frequency Waves, of which the following is a full, clear, concise,and exact description.

The present invention relates to the transmission and control of currentwaves for signaling or other purposes. The invention relates also tomultiplex transmission of the type employing current waves of differentfrequencies each of which waves is controlled in accordance with signalsor other impulses to be transmitted.

A feature of the invention lies in an improved modulating arrangement.Another feature lies in providing a centralized source of high frequencywaves and method and means whereby waves from said source are controlledto effect multiplex transmission in both directions over a line orsimilar system.

In systems heretofore used it has been customary to impress a highfrequency wave and low frequency signaling currents separately upon acontrol device or modulator,

and in another circuit suitably associated with the modulator to derivethe combina- 39 tion frequencies. The only high frequency wavesimpressed on the line or-transmission circuit in the process oftransmission were those transmitted through the modulator itself. I

In the present invention the same circuit which impresses the highfrequency currents upon the modulator may serve to convey the modulatedcurrents to the line or common transmission circuit, and it is notnecessary, therefore, to provide a source of high frequency Waves from aseparate high frequency circuit for each modulator dis tinct from thecircuit for carrying the 1110Cl1llated waves. The high frequencies areimpressed froin the generatingsources upon the line or commontransmission circuit, and each modulator derives its supply of highfrequency from the line or common trans mission circuit and feeds backthrough the same circuit the modulated current when the signalingcurrents are also impressed upon the modulator. By associating the highfrequency sources with the line or common transmission circuit insteadof with the separate modulators the present invention makespossible theuse of centralized sources of high frequency waves for supplying anumber of modulators. These wave sources may be located at someconvenient point on the line and at a distance, if desired, from thetransmitting sets to which they supply energy.

Other features and objects of the invention will appear from thefollowing description together with the accompanying drawings, of whichFigs. 1 and 2, when placed side by side, illustrate diagrammatically acomplete two-channel high frequency telephone system, and Fig. 3 showsmodified arrangement.

Referring first to Figs. 1 and 2, the main line 1 is shown asterminating at two stations, one of which has transmittingsets T and Tand receiving sets R and 3,, and the other of'which has sets R and R andT and T cooperating respectively with the transmitting and receivingsets of the first station. For enabling simultaneous twowaycommunication, the line 1 is provided with the usual conjugate coils iand 5 and harmonics from the base frequency wave from source 6. Thedistorted and amplified wave from the relay 9 is transmi ted through thecoupling 10 and impressed upon the amplifier 11, the output circuit ofwhich includesthe resonant circuits 12 and 13. In the case of a systememploying more than two communication channels, additional circuitssimilar to 12 and 13 would be provided forderiving still other harmonicsfrom the base frequency wave. Individual amplifiers 14: and 15 areprovided for the harmonic waves which are selected by the circuits 12and 13 respectively. I

Coupled to the amplifiers 1d and 15 are the coils l6 and 17 which areincluded serially with a coil 1.8 coupled to the coil 7in the circuit ofsource 6 and the circuit including coils 16, 17 and 18 is finallyconnected across he terminals of the output lin winding Between the coil18 and tne remainder of the circuit there is inserted a filter 19 soproportioned as to transmit only the base frequency current from thesource 6, and to prevent frequencies impressed upon coils 16 and 17 fromreacting on the circuit of source 6. There are, therefore, waves ofthree different frequencies simultaneously impressed upon the main line1, one of which waves is the wave directly transmitted from the source 6and the other two of which have frequencies which are harmonics of thebase frequency. Also connected across the terminals of the input coil ofthe line coupling 1, are filters 20 and 21. The filter 20 is designed toadmit to the coil 22 a band of frequencies sufiicient in breadth toinclude one of the high frequency waves iii-pressed on the input coil 1,together with the side bands of frequencies which result frominodulating said wave in accordance with speech. For the particularsrelating to the design and construction of'such a filter reference maybe had to the patent to G. A. Campbell No. 1,227,113, issued May 22,191?. This ilter prevents currents of all other frequencies fromreaching the coil 22 on account of the hi 'hly attenuating which itpossesses for foreign freouencies. @ne of the high frequency waves wimpressed on the main line 1 fro fiers 1 1 or 15 is therefore transm c tcoil 22 by the filter 20, and virtue 0 coupling with the coil 23 sets upcorr spo ing voltages across the terminals of coil The latter coil isincluded in the outp L plate circuit of the modulator M, which also 2 1and the plate or anode 25. Due to the potential variations induced inthe coil23, th re will be a circuit of the modulator M the magnitude ofwhich current will depend upon the im pedance of this circuit.Practically the whole of this impedance lies in the modulator tubeitself, and this ii pedance, in turn, depends upon the potential. of thegrid 26 which is determined by voice currents in the circuit 27 due tospeech waves directed against the microphone 28. By speaking into themicrophone 28, which forms a part of the transmitting set T varia l ofthe frequency of the wave admitted by the filter 20 from the main line 1will be setup in the 'output coil 23 and will be impressed through thefilter 20 upon the line 1. The action of the modulator M, is apparentlythe same as though the high frequency waves were impressed upon theplate circuit through a separate coupling, but by virtue of the presentarrangen'ient no such s parate coupling is needed, and, sta ed, the highand 1), respectively.

current flow in the output frequency may be derived from thetransmission line itself.

The transmitting set T differs from that just described only in thefrequency ofthe wave whichis employed for transmission; that is, theIlltfil' 21 is so proportioned as to transmit a different high frequencyvoice modulated wave. The modulated high frequency waves from themodulators M and M are, therefore, impressed through the ling 4 upon themain line 1 and are transmitted to the distant station indicated in Fig.2. Bridged across the line at this station is the coil 30 to which arecoupler filters 31, 32 and which are or may be identical respectivelywith the filters 19, 20 and 21, shown at the transmitting station.Frequencies from the transmitting sets impressed upon the coil 30 are,therefore, selectively transmitted by the filters 32 and 33, associatedwith which are the detectors D, These serve to detect the speechcomponent of the modulated waves and render the waves receivablerespectively in the telephone receivers 3 1- and The lil sis 20, 21, 31,32, 33, F and F, are each composed of a plurality of sections. The end sctions of filters 20 and 21, which are adjacent to the common line 1,are con nected together in series with respectto line. These endsections form paths of low inipedance to currents of all frequenciesexcept those which the filter is designed to pass. Similarly the endsections of filters 31, 32 and 33 as a group and those of filters 1 antT as a group are connected together in As already stated, the source 6supplies energy for all of the high frequency waves used to transmit inboth directions through the system being described. For transmitting inthe direction opposite to that above described, two waves, which may ormay not have the same frequencies as those employed by the transmittersT and T are derived from the same source 6. The wave of base frequencytransmitted over the line is selectively transmitted through the filter31, as described, and is impressed upon the distorting relay 36 for thepurpose of producing harmonics. Coupled to the distorting relay 36 is anamplifier 37 containing in its output circuit the resonant circuits 12'and 13 respectively. and these are coupled to the separate amplifiers 38and 39, which supply the amplified currents of harmonic frequenciesthrough the coils e0 and all to the output line coil 5. The transmittingsets T and T, are associated through the respective modulators M and Mand the band filters F, and F, with the main line in asimilar manner tothat described in connection with the transmitting sets T and T6, thesame harmonics are employed (ill for transmission in both directions,the lilters F and F, may be identical with the filters and 21. from thetransmittingsets T and T, are impressed upon the main line 1, and are received at the station, shown in Fig; 1, where they-are separated by thefilters F and IQ to be separately received. The detectors D and D renderthe wave receivable in the receivers shown for the receiving sets R andR respectively. i I

By virtue of the conjugate arrangements of the coils 4 and 5 andcorresponding nets 2 and 3, the modulated waves produced in each stationare prevented from affecting the receiving sets located in the samestation, according to standard practice. Referring now to Fig. 3, thereis shown a main line 42 which may be provided with branches 48 and 49,as may be desired. The main line is shown as provided with con jugatecoils 4-3 and'net-work 44c and the branches may be similarly provided.At some convenient point on the main line 42, for instance in a centralstation, maybe located the wave sources 45, i6 and 4: having frequenciesf, f and j, which sources may be separated or may, be related in somesuch way, as described in connection with the other figures. Thesesources supply waves of their respective frequenc'es to the main line42, which waves are made available for all of the transmitting setslocated upon the line. A part of the energy of each wave will find itsway into the transmitting and receiving side of the station shown at theleft of the line. matically indicated as F, F and F serve to convey tothe respective modulators the waves that are to be utilized by the transmitting sets, three of which are indicated. Modulated high frequencycurrents from these modulators M, M and M are in turn impressed throughthe coils upon themain line 42, and may be received at such of thedistant stations indicated on the respective branches l8 and 49 as areadapted. to receive and detect it. The balanced relation between thetransmitting and receiving sides of each station, however, will preventthe,

modulation component, resulting from the interaction of each highfrequency ,wave with the signaling currents, from reaching the receivingside of the same station. Modulated waves impressed upon the line atanother station, however, will, in the usual manner, be impressedthrough. the filters 1*, F and F upon the detectors ;D, D and D and willbe received in the respective receivers.

While the invention has been illustrated and described with reference toa particular The modulated waves The band filters diagrannimoressin onsaid line a luralitv of hi h- J. 2: t b

frequency waves of different frequencies,

and means for modulating each of said waves in accordance with signalsto be transmitted over said line, the modulating means for each of saidwaves comprising a modulator, a band filter for diverting one of saidwaves from the line to said modulator, a coupling for impressing saidwave upon said modulator, a circuit for also impressing signalingcurrent on said modulator to modulate said high-frequency wave, saidcoupling and selective circuit serving also to impress the modulatedwave upon said line.

2. In a signaling system, a line, a source of high-frequency wavessupplying waves to said line, and means for impressing signal-modulatedhigh-frequency waves upon said line, said means comprising a modulatorhaving an input circuit for signaling current and an output circuit bothfor the high-frequency waves to be modulated and for'the high-frequencywaves modulated in accordance with said signaling current, a band filterconnected between said output circuit and said line, whereby said highfrequency waves are applied to said output circuit from said linethrough the medium of said band filter.

3. Ina signaling system, a line, a source of high-frequency waves forsupplying current thereto, a modulator for controlling said waves inaccordance with signals, means to connect said source of waves to saidline, and a band filter connected between said means and said modulatorfor transmitting selectively said waves to said modulater and thesignal-modulated wave from said modulator to said line.

4c- In a telephone system, a line, a source of sustained high-frequencywaves for supplying current to said line, a modulator havingmeanswhereby speech variations may be impressed thereon for modulatingsaid high-frequency waves, means to connect said at a station, andconjugate connections for making the receiving branch neutral as tocurrent impressed from the transmitting branch, sources of highfrequency waves for supplying current to said line, modulatorsassociated with said transmittting branch accordance with signals, andplurality of sectional band-pass filters connected between saidmodulators and said line, the end sections of said band-pass filtersbeing connected in series with each other.

7. in a telephone system, a line, aplurality of sources of sustainedhigh-frequency waves for supplying current to said line, a plurality ofmodulators having means whereby speech variations ma be impressedthereon for modulating a high-rreqency wave, and a plurality ofsectional band-pass filters between said modulators and said line, theend sections of said'band-pass filters being connected in series witheach other.

8. In asignaling system, a line, a plurality of sources ofhigh-frequency waves ior suppl ing current to said line, a plurality ofmodulators "for controlling said waves in accordance with signals, and aplurality of sectional band-pass filters, one of said filters beingconnected between said line and each modulator for transmittingselectively a high-frequency wave to said modulator and nal modulatedwave from said modulator to said line, the end sections adjacent to saidline or all of said filters being connected in series with each other.

9. In a telephone system, a line, a source of sustained high-frequencywaves for supplying current to said line, a modulator having meanswhereby speech variations may be impressed thereon for modulating a highfrequency rave, and a plurality of sectional band-pass filters, onefilter being connected between each modulator and said line forimpressing a high-frequency wave upon said modulator to be modulated inaccordance with, speech and for transmitting the speech modulated wavefrom said modulator to said line, the end sections of said filtersadjacent id line being connected in series with l0 SZlrxL each other.

10. A high frequency wave signaling system comprising a line havingstations, a plurality of transmitting and a plurality of receivingbranches for said line at said station and conjugate connections formaking the receiving branches neutral as to current impressed from thetransmitting branches, a plurality of sources of high-frequency wayesfor supplying current to said line, a modulator associated with each ofsaid transmitting branches and controlled by signals, asectionalband-pass filter between each modulator and said line adaptedboth for impressing said waves upon the respective modulators and fortransmitting the resultant modulate-d waves from said modulator to saidline, the end sections of said filters adjacent to said line beingconnected in se ries with each other, and receivers at another stationfor the waves so modulated.

11. A high-frequency wave signaling system comprising a line havingstations, a plurality of transmitting and a plurality of receivingbranches for said line at a station and means to connect saidtransmitting and receiving branches to said line, a plurality of sourcesof high-frequency waves for supplying current to said line, a modulatorassociated with each transmitting branch and controlled by signals, asectional bandpass filter connected between said modulator and said lineadapted both for impressing said waves upon the connected modulator andfor transmitting the resultant modulated waves from the connectedmodulator to the line, means to connect the end sections of said filtersadjacent to said line in series with each other, and receivers atanother station for the waves so modulated 12. In a multiplex signalingsystem, a

plurality of sources of high-frequency waves, a plurality of means tomodulate said high-frequency waves in accordance with signals, a commontransmission circuit, and a band-pass filter connected between eachmodulating means and said transmission circuit comprising a plurality ofsections, the end sections being connected in series with each other.

13.111 a multiplex signahig system, a plurality of sources ofhigh-frequency Waves, plurality of means to modulate said high-frequencywaves in accordance with signals, a common transmission circuit, asectional band-pass filter connected between each modulating means andsaid transmission circuit, and means to connect the end sectionsadjacent to said transmission circuit in series with each other.

14-. In a multiplex signaling system, a. plurality of sources 0thigh-frequency waves, a plurality of thermionic vacuum tubes each havingan. anode, a cathode and an impedance controlling element or grid, asource of signaling current, means to sup ply said high-frequencycurrent and said signaling current simultaneously to said vacuum tubesto produce high-frequency current modulated in accordance with signalingcurrent, a common transmission circuit, a sectional band-pass filterconnected between each vacuum tube modulator and said transmissioncircuit, and means to conmet the end sections nearest said transmis sioncircuit together in series.

15. A common transmission circuit, a plurality of channels associatedtherewith, means for transferring currents of a given range offrequencies between one of said channels and said circuit and currentsof a different range of frequencies between each of the other channelsand said circuit comprising a band filter connecting each channel tosaid circuit and having a transmission range such that itfreely passescurrents of the range of frequencies supplied from the associatedchannel, said band filters having ter inations connected in series insaid circuit, the termination of each filter ofi'ering low impedance tocurrents Within the frequency transmission range of the other filters.

16. A common transmission path, a plurality of channels each adapted totransmit currents of differ nt frequency from those transmitted by theother channels, and a separate band filter connecting each channel tosaid path, the terminations of said filters electrically adjacent saidpath being connected in series.

17. In a modulating circuit, an electric discharge modulator tube havingan anode, a cathode and a grid or impedance control element, a circuitfor impressing signal variations across the grid and cathode of saidtube, a source of waves to be modulated, a circuit for impressing Wavesfrom said source across the anode and cathode of said tube, a bandfilter included in said latter circuit having a selective transmissionrange such as to include the frequencies of the Waves to be modulatedand at least a portion of the resulting signal-modulated components, andan outgoing circuit for the modulated Wave connected to said modulatortube through said filter.

18. In a modulating circuit, an electric dischargetube modulator havingan anode, a cathode and a grid or impedance control element, means toimpress speech variations across the cathode and grid, a source of Wavesto be modulated, a band filter having a selective frequency transmissionrange such as to include the frequency of the Wave from said source andat least a portion of the frequency components of the resultantmodulatedWave, but excluding speech frequencies, a circuit including said bandfil e: for impressing Waves from said source across the anode andcathode of said tube, and an outgoing circuit for the modulated Waveconnected to said modulator through said filter.

In Witness whereof, I hereunto subscribe my name this 26th day ofSeptember EDWARD o. SCRIVEN.

